Head to the left to find May/Brendan confronting Team Aqua members. You'll be fighting in a double battle with May/Brendan.
Team Admin Shelly and Team Aqua Grunt (Reward: p3,220)
After the battle, Team Magma will make an appearance as well. You'll escort the Professor back to Fallarbor Town. He will give you TM23 Smack Down as reward for saving him. May will invite you to go back to Mauville with her.